Interstellar Probe: The Compelling Science Case, Strawman Payload and Resources

Venturing on to an escape trajectory beyond the solar system offers science discoveries of different proportions that will naturally bridge planetary, helio- and astrophysical disciplines by putting our solar system and heliosphere in the context of the increasing number of other exoplanetary systems and astrospheres detected. Science discoveries enabled by an Interstellar Probe include new understanding of the global structure of our heliosphere and its interaction with the Local Interstellar Medium (LISM), observations of the circum-solar dust disk providing insights in to planetary formation processes, discoveries of unexplored Kuiper Belt Objects such as Quaoar, transit observations of solar-system planetary atmospheres to provide standard candles to aide in the interpretation of exoplanetary observations, and possibly the first flyby observations of a hypothetical Large Trans-Neptunian Planet.

The first explicit Interstellar Probe will target up to 1000 AU distance from the Sun in 50 years, which requires asymptotic speeds of 20 AU/year. Mission scenarios include a launch on an SLS Block 1B, assuming a New Horizons-like spacecraft with a reverse Jupiter Gravity Assist followed by an Oberth Maneuver close to the Sun requiring a heat shield, building on the flight experience of the Parker Solar Probe heat shield. In the context of flown payload-to-spacecraft-mass fractions, the allowable payload mass is about 40 kg (including 30% reserve). Similarly, power supplied by a general-purpose Radioisotope Thermoelectric Generator leaves about 40 W for a science payload. This illuminates the criticality of light-weight, low-power, compact instruments and innovative, yet reliable payload solutions.

Here, we provide an overview of the results of recent studies of science targets, instrumentation versus resources. We discuss the important trades that were made between science return and mission design, such as fly-out direction and KBO targets. The derived performance requirements are presented in light of the challenging aspects of the mission, such as the high flyby speed. We summarize the current state of instrumentation and the development needed to achieve the strict resource allocations.